Available online at www.sciencedirect.com Planetary and Space Science 50 (2002) 1345–1353 www.elsevier.com/locate/pss TheSMART-1X-raysolarmonitor(XSM):calibrationsforD-CIXSand independentcoronalscience J.Huovelin a ; * ,L.Alha a ,H.Andersson c ,T.Andersson b ,R.Browning e ,D.Drummond e , B.Foing g ,M.Grande e ,K.H am al ainen b ,J.Laukkanen b ,V.L ams a c ,K.Muinonen a ,M.Murray d , S.Nenonen c ,A.Salminen c ,H.Sipil a c ,I.Taylor d ,O.Vilhu a ,N.Waltham e ,M.Lopez-Jorkama f a Observatory, University of Helsinki, P.O. Box 14, FIN-00014 Helsinki, Finland b X-ray Laboratory, Department of Physics, P.O. Box 9, FIN-00014 Helsinki, Finland c Metorex International Oy, P.O. Box 85, FIN-02631 Espoo, Finland d Metorex Inc., Princeton Crossroads Corporate Center, 250 Phillips Boulevard, Ewing, NJ 08618, USA e Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK f VTT Automation, P.O.Box 1303, FIN-02044 VTT, Finland g ESA Space Science Department, ESTEC/SCI-SO, Postbus 299, 2200 AG Noordwijk, The Netherlands Accepted 27 June 2002 Abstract The X-ray solar monitor (XSM) is a calibration instrument of the demonstration of compact imaging X-ray spectrometer (D-CIXS) experiment,withaseparateSilicondetectorunitontheSMART-1spacecraft.Thenon-imagingHPSiPINsensorhasawideeld-of-view (FOV) to enable Sun visibility during a signicant fraction of the mission lifetime, which is essential for obtaining calibration spectra fortheX-rayuorescencemeasurementsbytheimagingD-CIXSspectrometer.Theenergyrange(1–20keV),spectralresolution(about 250 eV at 6 keV), and sensitivity (about 7000 cps at ux level of 10 -4 Wm -2 in the range 1–8  A) are tuned to provide optimal knowledgeabouttheSolarX-rayuxontheLunarsurface,matchingwellwiththeactivatingenergyrangefortheuorescencemeasured by D-CIXS. The independent science of the XSM will also be valuable, since the XSM energy range is very sensitive to solar ares. The countrate during the top of an X1 are will be about 35 times higher than the average quiescent countrate at solar maximum. The relativeincreasewillbethesameforanM1areduringtheSMART-1mission,whichwillbeclosertothenextsolarminimum.Since the XSM will observe the Sun as a star, and the energy range and spectral resolution are close to those of present astronomical X-ray satellites(e.g.,XMM-Newton,ASCA,Chandra),wewillobtainanX-raydatabaseoftheSunwhichcanberelatedwiththestellarX-ray observations more easily than the data from present solar X-ray instruments. In this publication we give a detailed description of the design, performance, and tasks of the XSM instrument, and view the science perspectives. ? 2002 Elsevier Science Ltd. All rights reserved. 1. Introduction SMART-1isatechnologydemonstrationmissionofthe ESA.Itisscheduledforlaunchasasecondarypayloadon anAriane5rocketwithinthetimewindowofayearfrom October 2002 (Foing et al., 2002). The primary purpose of SMART-1 is to show that the solar electric propulsion systemiscapableofmanoeuvringandthrustingaspacecraft duringlongdeepspacemissionsinthesolarsystem. ∗ Corresponding author. E-mail address: juhani.huovelin@astro.helsinki. (J. Huovelin). SMART-1 will also carry a small scientic and tech- nologypayload,includinganX-rayinstrumentforprobing and analysing chemical composition of solar system bod- ies.ThereisanX-rayinstrumentpresentlyoperatingonthe NEARmissionofNASA(Goldstenetal.,1997),whichhas a solid state Si-detector as one of the solar spectrometers while the main X-ray detector observes the surface of the Erosasteroid(Trombkaetal.,1997).TheSMART-1X-ray instrument has basically a similar task, with the Moon as themaintarget.Theinstrumentincludesthemaindetector, D-CIXS (Demonstration of Compact Imaging X-ray Spec- trometer) described in detail by Grande et al. (2002),and 0032-0633/02/$-see front matter ? 2002 Elsevier Science Ltd. All rights reserved. PII:S0032-0633(02)00127-7